Crane boom extending, retracting and cooperative latching arrangement

Abstract

To reduce the weight and increase the lifting capacity of a multi-section telescopic crane boom, a single hydraulic cylinder for the full extension and retraction of individual boom sections is anchored in the relatively stationary boom base section. A sled structure surrounding the single cylinder and moving therewith has guided engagement through plates fixed to the movable boom sections at or near their rear ends. Driving finger mechanisms on opposite sides of the sled are biased toward driving engagement with the plates of the movable boom sections and are retractable into chambers of the sled. A cooperative locking pin operating assembly for the movable boom sections is fixed on the forward end of the boom base section and includes power retracting devices which operate mating retracting cranks and locking pin sets individual to the movable boom sections when the retracting cranks are aligned beneath the power retracting devices. The movable boom sections are equipped near their outer and inner ends with locking receivers for said locking pins.

I claim: 
     
       1. A crane boom comprising plural telescoping boom sections which are individually movable relatively and a boom base section which is relatively stationary and in which all of the movable boom sections may be nested telescopically, each movable boom section having locking detent means thereon near its outer and inner ends, a single power cylinder anchored within the boom base section and being extensible and retractable longitudinally of the boom to fully extend and fully retract selectively any individual movable boom section, each movable boom section having a fixed driving member near its rear end, cooperative driving means for said fixed driving members on said cylinder and moving therewith and being biased toward engagement with the fixed driving members, power means moving with said cylinder to retract said cooperative driving means from said fixed driving members to enable the driving means to pass by certain fixed driving members, a locking assembly common to the movable boom sections and being fixed to the boom base section, plural independently operable locking elements individual to the movable boom sections on certain of the movable boom sections and moving therewith and being biased toward engagement with said locking detent means of adjacent movable boom sections, and plural selectively operable power means on said locking assembly to retract said locking elements of any movable boom section from the locking detent means of an adjacent boom section so that the latter may be fully extended or retracted by said single power cylinder. 
     
     
       2. A crane boom as defined in claim 1, and said fixed driving member of each movable boom section comprising a plate near the rear end of such section having a guide opening therethrough, said cooperative driving means on said cylinder and moving therewith comprising a sled structure secured to the cylinder and adapted for sliding engagement on bottom walls of said movable boom sections, said sled structure having guided engagement within said guide opening of said plate of each boom section, and an extendable and retractable positive driving device for said plate of each boom section selectively on at least one side of the sled structure, spring means biasing said driving device toward engagement with said plate, and power means on said sled structure connected with the driving device to retract it against the spring means so that the driving device may clear plates of non-selected movable boom sections when a particular chosen boom section is undergoing full extension or full retraction. 
     
     
       3. A crane boom as defined in claim 2, and said driving device comprising a pair of intermeshing drive fingers pivotally attached to the sled structure and defining in their biased positions a driving recess which captures an edge of said plate of a selected movable boom section. 
     
     
       4. A crane boom as defined in claim 3, and said fingers having outer side edges inclined to the axis of said boom and cammingly engaging said edge of said plate to depress said fingers against said spring means whereby the edge of said plate may snap into said driving recess. 
     
     
       5. A crane boom as defined in claim 4, and said fingers having pivots on said sled structure offset from the side walls of said driving recess whereby pressure of said plate on said side walls tends to force said fingers further into driving engagement with said plate. 
     
     
       6. A crane boom as defined in claim 5, and overtravel limiting means for said fingers in their biased direction. 
     
     
       7. A crane boom as defined in claim 1, and said locking detent means comprising openings in the bottom wall of each movable boom section, and said locking elements on certain of the movable boom sections comprising locking pins adapted to enter said openings when moved into registration therewith. 
     
     
       8. In a crane boom, a relatively stationary boom base section and a plurality of relatively movable boom sections which are telescopically nestable in the base section when retracted and extendable therefrom, means to fully extend and fully retract each movable boom section selectively to produce desired boom configurations, a locking mechanism common to all of the movable boom sections fixed on the boom base section near its forward end, movable locking elements carried by certain of the movable boom sections near their forward ends and being biased toward locking positions, with adjacent movable boom sections, the movable boom sections having locking receivers for said locking elements near their forward and rear ends, and power means on said locking mechanism operable to selectively retract the locking elements from their locking positions to enable the full retraction or full extension selectively of the movable boom sections by the first-named means. 
     
     
       9. In a crane boom as defined in claim 8, and said locking mechanism comprising a support fixed to one side of the boom base section, plural selectively operable power cylinders on said support, said movable locking elements comprising locking pins at stepped elevations on the movable boom sections, and a corresponding number of rocker shafts on the movable boom sections operatively connected with said locking pins and adapted when moved adjacent to said power cylinders to be rotationally operated thereby selectively. 
     
     
       10. In a crane boom as defined in claim 9, and control valves individual to said power cylinders on said support to enable selective individual operation of the power cylinders. 
     
     
       11. In a crane boom as defined in claim 10, and said power cylinders on said support comprising pneumatic cylinders, one portion of said support defining a compressed air manifold, and conduit means connecting said manifold with said control valves and connecting said control valves with said pneumatic cylinders. 
     
     
       12. In a crane boom as defined in claim 11, and said control valves comprising solenoid operated valves. 
     
     
       13. In a crane boom as defined in claim 9, and compression springs engaging said locking pins to bias them toward locking engagement with said movable boom sections, and retracting arms for said locking pins on said rocker shafts movably engaging the locking pins to retract them against the force of said compression springs. 
     
     
       14. In a crane boom as defined in claim 13, and projections formed of low friction material on the forward ends of the locking pins to reduce wear caused by sliding of the bottom walls of movable boom sections across the forward ends of the biased locking pins. 
     
     
       15. In a crane boom as defined in claim 9, and said locking receivers comprising rectangular locking openings formed in the bottom walls of the movable boom sections, and said locking pins being cylindrically formed and being of a size to enter said locking openings and having side notches near their forward ends adapted to receive edges of the rectangular locking openings. 
     
     
       16. A crane boom comprising plural telescoping boom sections which are individually movable relatively and a boom base section which is relatively stationary and in which all of the movable boom sections may nest telescopically, a fixed driving plate on each movable boom section near its rear end and having a guide opening formed therethrough, a single power cylinder anchored within the boom base section and being extensible and retractable longitudinally of the boom to fully extend and fully retract selectively the movable boom sections, cooperative driving means on said single power cylinder and moving therewith and having guided engagement within said guide openings, the cooperative driving means including at least on one side thereof extendable and retractable positive drive elements for said plates biased toward driving engagement therewith, power means on said cooperative driving means to retract said positive drive elements from said plates, and additional selectively operable power means on the boom base section and movable boom sections to releasably lock the latter in fully extended and fully retracted positions. 
     
     
       17. A crane boom as defined in claim 16, and said cooperative driving means comprising a sled structure on said single power cylinder adapted for sliding engagement on the movable boom sections, and said positive drive elements comprising interengaging spring biased drive fingers pivoted to the sled structure and in their biased positions defining a recess for capturing and driving said plates selectively outwardly or inwardly on said boom. 
     
     
       18. A crane boom as defined in claim 17, and said power means on said cooperative driving means comprising at least one power cylinder operatively connected with said fingers to retract the latter to a position on the sled structure inwardly of edge portions of the plates defined by the guide openings.